[Cytokine secretion in whole blood of healthy subjects following oral administration of Urtica dioica L. plant extract].

Twenty healthy volunteers ingested for 21 days 2 capsules b.i.d. of an IDS 23/1 containing nettle leaf extract (Rheuma-Hek). Before and after 7 and 21 days the basal and the lipopolysaccharide (LPS) stimulated tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) concentrations were measured ex vivo. In vitro the effects of IDS 23/1 on the release of these cytokines were determined. Additionally basal interleukin-4 (IL-4) and interleukin-10 (IL-10) levels were recorded. Orally taken the test drug has ex vivo no effect on basal levels of TNF-alpha, IL-1 beta, IL-4, IL-6 or IL-10 which were always below detection limits. After 7 and 21 days ingestion ex vivo a decrease of LPS stimulated TNF-alpha release of 14.6 and 24.0%, respectively, was observed. IL-1 beta was reduced for 19.2 and 39.3%. In vitro IDS 23/1 added to whole blood resulted in an exceeded inhibition of LPS stimulated TNF-alpha and IL-1 beta secretion which correlated with the duration of the drug ingestion. Using the highest tested IDS 23/1 concentration the inhibition reached 50.5 (day 0) to 79.5% (day 21) for TNF-alpha and 90.0 (day 0) to 99.2% (day 21) for IL-1 beta, respectively. IDS 23/1 induced a pronounced release of IL-6 in absence of LPS only in vitro. The detected IL-6 concentrations were comparable to those after LPS stimulation, additive effects could not be observed. The absence of detectable IL-6 concentrations in whole blood ex vivo after oral ingestion of the tested drug as well as the differences in the inhibition patterns for TNF-alpha and IL-1 beta ex vivo and ex vivo in vitro suggest that the extract contains different pharmacological effective compounds with varying bioavailabilities.